How To Cap A Variable?

VEX V5 Technical Support
#1

So I’m using a counting integer to set the position of a servo. The problem is once the variable gets to big the servo shoots back to the 0 position. Does anyone know how to set a range for a variable or set a min/max for it?

#2

Use an if/else, if you want a min of say 20 and a max of 100, do something like if 20<value && value<100 then variable = whatever the value is, then else if 20>value then variable =20 and else variable =100. I’m not an expert on servos but I am a coder and that general setup works for mins and maxes

#3

The way my program is set up wouldn’t work like that. I just need to know if there is like a command that restricts the integer from passing a certain value. Appreciate the suggestion though!

#4

Make a “command” by making a function called “min” that accepts 2 ints as parameters, and returns the smaller one. Every time you want to update the variable, call the min function with the new value and the cap as parameters.

#5

Below is a function that my teams use. It works well with motors because the value can be either positive or negative.


int Max(int value, int maxValue){
	return (abs(value) <= abs(maxValue)) ? value :
	    (value > 0) ? maxValue : -maxValue;
}

//Example usage
		int x = Max(100,50);  //Returns  50
		int y = Max(-100,50); //Returns -50 (because the first value is negative)
		int z = Max(40,50);   //Returns  40
		int k = Max(-40,50);  //Returns -40
                int motor1 = Max(controlVal, 127);  //limits the top speed to 127 regardless of direction

Edit: Typo

#6

So long as you are looping through the code, a simple if statement should do the trick. Maybe post the relevant code here?

#7 
if(abs(var) > max)
{
var = max * sgn(var)
}
#8

Ideally you’d encapsulate a variable and never allow directly setting it so you can maintain the constraint.

#9

Nice use of the


sgn

function. Time to refactor.


int Max(int value, int maxValue){
	return (abs(value) <= maxValue) ? value : maxValue * sgn(value);
}
#10